In a gas turbine installation, while it is in operation, exhaust gas has to be extracted from the gas turbine and discharged. It is necessary, as a rule, to erect a special chimney for this purpose.
A chimney of this kind is also necessary, and has to be erected separately, when the gas turbine installation is extended by way of a steam generator to form a gas and steam turbine installation (combined-cycle installation). Here, the exhaust gas from the gas turbine is utilized for the generation of steam to be used by the steam turbine. A chimney is also necessary when gas turbine operation is desired, even before the completion of the entire combined-cycle installation (“preferential gas turbine operation”).
A bypass chimney, as it is known, is erected and used for the discharge of the exhaust gas from the gas turbine, at least until the components relating to the steam turbine are installed and ready for operation. Once the combined-cycle installation is completed, the exhaust gas from the gas turbine can be introduced into a waste-heat steam generator, thereby obviating the need for the bypass chimney. The erection of a bypass chimney of this kind and its possible dismantling after the completion of the combined-cycle installation are complicated.